VMM: fixed out of memory guru meditation for large memory guests (bug #7586)

VMM: fixed a guru meditation related to large pages

VMM: use new VT-x feature to keep the guest from hogging the CPU

Snapshots: implemented deleting the last remaining snapshot while the VM is running

GUI: perform the checks for exceeding the size limit of the host file system and for broken asynchronous I/O on older Linux kernels with ext4 / xfs file systems not only when starting the VM from scratch but also when starting from a saved state